The present disclosure relates to a diagnosis system for monitoring the status of a switchboard, and more particularly, to a diagnosis system for monitoring the status of a switchboard that may early detect a sign experiencing insulation breakdown due to deterioration or the weakening of mechanical coupling by internal and external factors (electrical, thermal, chemical stress and vibration, and environmental factors) of the switchboard, and eventually leading to an accident to prevent the spread of the accident.
Many electrical apparatuses for power conversion, transmission and measurement are arranged in a switchboard. However, these electrical devices may experience insulation breakdown due to deterioration or weakening of mechanical coupling by internal and external factors (electrical, thermal, chemical stress and vibration, and environmental factors) and eventually cause an accident.
In a typical method for the status diagnosis of the switchboard, a single partial discharge sensor or temperature sensor module is attached for monitoring.
The partial discharge sensor is installed mostly as an ultra high frequency (UHF) sensor in the switchboard and detects an electromagnetic signal emitting when partial discharge PD due to the insulation deterioration of a mold transformer in the switchboard occurs. A detected partial discharge signal is processed through a dedicated data processing apparatus and whether the partial discharge signal has been generated and the size of the signal are transmitted to a higher diagnosis system.
The temperature sensor is attached to a busbar in the switchboard to measure the temperature of the busbar by using a contact type or non-contact type sensor, and a measured temperature is processed in its own unit module and transmitted to a higher diagnosis system. The higher diagnosis system diagnoses the status of the switchboard based on each of data transmitted.
In addition, many sensors are attached as a monitor device for preventing the trouble of the mold transformer in the switchboard and an earth-side high frequency current transformer (HFCT) sensor that is easily attached on a hot line is mostly used.
FIG. 1 depicts a method of measuring a partial discharge signal generated in a mold transformer in a switchboard by using a typical HFCT sensor.
Referring to FIG. 1, as insulation deterioration occurs in a mold transformer 1 installed in the switchboard, a PD signal 2 is internally generated.
The PD signal generated in the mold transformer 1 flows along an earth wire 4 connected to a transformer base 3.
The PD signal 2 flowing along the earth wire 4 is detected by the HFCT sensor 5, a measuring sensor to be displayed by an oscilloscope or a data obtaining device 6 that may check signals.
As such, since the PD measuring method using the HFCT attaches a sensor to the earth wire by using a clamp type and thus it is possible to install a sensor and measure a signal even in a hot line status, the PD measuring method using the HFCT is being widely used.
However, in measuring the PD signal flowing in the earth wire, the signal is weak and thus is easily affected by external noise, and it is substantially difficult to detect a signal due to a noise signal even if micro discharge occurs.
Thus, in diagnosing the status of the mold transformer in the switchboard, it takes long times to determine internal deterioration and in determining precise diagnosis and produce replacement periods.
As such, typical switchboard diagnosis systems include a single (partial discharge, temperature) sensor and thus are significantly insufficient for precisely diagnosing the status of the switchboard.
In the case of the UHF sensor, it is installed without a cover in the external box of the switchboard and thus vulnerable to external radiation noise. Also, in the case of a sensor having lower sensitivity among UHF sensors having different sensitivity characteristics, it is difficult to detect a discharge signal at an early status of insulation deterioration and in some cases, it is possible to detect the discharge signal after deterioration has significantly progressed and shortly before an accident.
When a PD signal is detected in the UHF sensor, there are many difficulties in determining whether the signal is a signal generated actually in an electrical apparatus or an external noise signal.
In the case of a temperature sensor installed at the center of the busbar, since the temperature of a conducted busbar is measured, there is a difficulty in measuring and diagnosing the temperature of an actually overheated electrical apparatus and a coupling part. The reason for this is because an accident due to overheat occurs more frequently on a bolt coupling part or a conductor-conductor coupling part than the center of the busbar.